Analysis of the action of maternal effect genes in the axolotl. Females homozygous for gene o produce eggs which can be fertilized and develop normally for a day, but invariably are arrested in early gastrula stage. Introduction of the normal allele of the gene at fertilization does not improve the the developmnt of these eggs. The failure of the embryos to develop beyond gastrulation is known to be due to a deficiency in the oocyte cytoplasm, which lead to a cessation of mitosis in late blastula stage and a failure of activation of nuclear RNA synthesi (normal embryos show a pronounced activation at this time). This interesting maternal effect is to be investigated further, as follows: a) Transplantation of nuclei from normal embryos, before and after RNA synthesis activation, into o/o eggs. Evidece indicates that normal nuclei prior to RNA activation do not improve the development of o/o eggs while post-activation nuclei lead to great improved development. This phenomenon will be further investigated. b) Transplantation of nuclei from o/o embryos into normal eggs. Present evidence indicates that nuclei from yong o/o blastulae promote normal development when transplanted ino normal eggs, but those from late blastule do not. This will be further investigated. Similar studies will be carried out on other maternal effect genes, as material become available. 2) Other projects include: A study of the effects of oocyte cytoplasm on the synthetic functions of transplanted somatic cell nuclei b) A study of the capacity of primordial germ cell nuclei to promote development in eggs lacking "germ plasm" c) A search for new mutations affecting the development of the axolotl.